Energy-limiting fuses have been supplied for many years for clearing fault currents in the region from 300 or 400 amperes to 50,000 and more amperes in one second or less. These fuses have difficulty in clearing smaller fault currents. To enhance fuse performance in the low current area series elements specially designed for low current clearing have been utilized alone or in combination. These elements include M-spots, auxiliary arcing elements, series integral expulsion sections, explosive charges, specialized alloys, gas-evolving spiders, and the like. However, all of these elements require additional cost and increase the complexity of the fuse.
Fuse manufacturers have also supplied blown fuse indicators with the energy-limiting fuses. These indicators typically include a strain wire running in parallel with the main fuse elements. The strain wire is solidly connected by soldering, braising, crimping, or winding the strain wire around the lead of the indicator. This type of solid connection makes handling of the striker pin assembly more difficult since the striker pin assembly is mounted on the spider assembly prior to incorporation of the spider assembly into the fuse. The striker pin assembly is exposed to damage in handling, requiring additional protective noses or guides, requires placing the strain wire through constricted openings, and requires that the entire striker pin assembly be pushed through the length of the insulated housing of the fuse.